JP 10-179608 A describes in FIGS. 1A-1F an example cartridge according to the related art. The cartridge includes: a cartridge body made of a resin and including a cylindrical portion 1 having two ends and an opening portion at one of the two ends and a nozzle body portion 2 disposed at the other of the two ends of the cylindrical portion 1 and provided with a nozzle; and a piston 13 made of a resin and disposed inside the cylindrical portion 1 of the cartridge body to push out a content contained in the cylindrical portion 1 through the nozzle. The thickness of the piston 13 is larger than the radial dimension of the cartridge. In the disclosed cartridge, a pair of piston-side tapered surfaces 15 are formed between an annular peripheral wall surface of the piston and a pair of circular end surfaces of the piston located on both sides in the thickness direction of the piston, and the pair of piston-side tapered surfaces 15 become smaller in radial dimension from the annular peripheral wall surface toward the pair of circular end surfaces.